Lubricating method for continuous casting

ABSTRACT

A METHOD OF LUBRICATING CONTINUOUS CASTINGS OF METALS, PARTICULARLY STEEL, WHICH COMPRISES INTRODUCING INTO THE CONTINUOUS-CASTING MOLD DURING CASTING A LUBRICANT CONSISTING OF A LUBRICATING OIL, SUCH AS RAPE OIL, IN WHICH ADDITIVES ARE INCORPORATED FOR INCREASING THE PROPORTION OF CARBON-CONTAINING CONSTITUENTS IN THE RESIDUES FORMED IN THE MOLD BY PYROLYTIC DECOMPOSITION.

United States Patent O LUBRICATING METHOD FOR CONTINUOUS CASTING Peter J. Koenig, Zumikon, Switzerland, assignor to Concast Aktiengesellschaft, Zurich, Switzerland No Drawing. Filed Mar. 21, 1969, Ser. No. 809,387 Claims priority, application Switzerland, Mar. 25, 1968, 4,395/68 Int. Cl. (310m 1/26 US. Cl. 252-37 6 Claims ABSTRACT OF THE DISCLOSURE A method of lubricating continuous castings of metals, particularly steel, which comprises introducing into the continuous-casting mold during casting a lubricant consisting of a lubricating oil, such as rape oil, in which additives are incorporated for increasing the proportion of carbon-containing constituents in the residues formed in the mold by pyrolytic decomposition.

The present invention relates to a method of lubricating continuous-castings, for improving the cast products, by introducing an improved lubricant into the continuouscasting mold.

BACKGROUND In continuous casting lubricant is introduced in the mold to ensure that the casting will slide through the mold satisfactorily. To be suitable, the lubricant must reduce the friction between the wall of the mold and the surface of the casting, but should not adversely affect the quality of the cast product.

At present the preferred lubricants are vegetable oils; mineral oils and liquefied paraffins are also frequently used, but these lubricants have several drawbacks.

Vegetable oils are usually expensive to use. In addition, the use of major quantities of vegetable oils introduces the risk of increased absorption of hydrogen by the steel and this depreciates the quality of the casting, for instance by causing the appearance of pores in or directly below the surface. Mineral oils, which like parafiin oil are frequently used due to their lower cost, have the drawback that their lubricating effect is often insufficient and that their combustion is accompanied by the formation of a sooty flame which obscures the visibility of the mold interior.

Liquefied paraffins are also unsatisfactory because rather large quantities are required and because special arrangements must be made to keep them liquid in the feed pump and pipes. And, particularly when casting different grades of stainless steel, an undesirable cementation of the surface zone often results.

For reasons of economy as well as of maintaining the quality of the cast product it is therefore desirable to use the minimum amount of lubricant although the resultant high friction may cause the casting to stick in the mold. This leads to the appearance of surface flaws and cracks and may even cause break-throughs.

It has therefore been proposed to introduce additives into the liquid lubricant to improve its lubricating effect on the casting. Graphite has been suggested as a possible solid additive. However, graphite forms a sediment and leaves deposits in the pipes of the lubricant supply system. This interferes with accurate metering of the lubricant; it also prevents uniform distribution of the graphite and causes friction so that portions of the casting tend to stick and cause cracks which may result in break-throughs.

OBJECT It is an object of the present invention to provide a method of lubricating continuous-castings as they" are "ice formed in a mold by introducing into the mold a lubricant containing at least an additive, which lubricant avoids the above-described drawbacks, particularly those of high lubricant consumption and of impairing the quality of the cast product.

DESCRIPTION OF THE INVENTION It is believed that the residues formed by pyrolytic decomposition inside the mold have an important influence upon the lubricating effect, and in accordance with the foregoing object the lubricating method of this invention comprises introducing into the mold a lubricant containing additives which will raise the carbon content of the residues formed by pyrolytic decomposition.

The lubricant of this invention consists of at least two components. The principal component, which may have a lubricating function, serves as a carrier for other components, namely, for the additives. The principal component may be a conventional lubricant oil. The suitable lubricating oil contains unsaturated organic compounds, such as appropriate fatty acids or their glycerides, which cannot be easily decomposed into readily volatilized components because their molecules have been linked by suitable additions or catalysts at room temperature, elevated temperature or during pyrolysis by condensation. Alternative principal components of the lubricant may be binary, ternary or higher mixtures of mineral oils and vegetable or animal oils, as well as mixtures of unsaturated natural or synthetic fatty acids or oils.

To these principal components may be added additives which are soluble in the conventional lubricating oil and which increase the carbon containing content of the residues when at least partial decomposition takes place in the mold at the high temperatures involved.

The preferred principal component of the lubricant is rape oil, or its practical equivalent colza oil, which possesses a high lubricity besides burning with a nearly smokeless flame.

The purpose of the additives is to increase the proportion of carbon-containing residues that form by pyrolysis and thus to improve the normal lubricity of the principal component alone, so that the lubricant substantially prevents sticking of the skin of the casting to the walls of the mold. A suitable addition is preferably lead naphthenate. It has been found, for example, that an addition to rape oil of 0.53% of lead napthenate having a lead content of 30% will raise the carbonization factor (which indicates the quantity of residue formed by pyrolysis) from 0.5% to 0.98%. This increase in the quantity of residue, particularly of the carbon-containing part of the residue, improves substantially the lubricating efiect. Consequently, less lubricant is required. This reduces the cost of properly lubricating the mold and also reduces other undesirable secondary effects of previously used lubricants on the quality of the cast steel, such as hydrogen absorption.

Further suitable additives can be used from the group of metal naphthenates and it is evident that, within the scope of this invention, these naphthenates can be used alone and in combination. Preferably cobalt and/or manganese naphthenate is added to the principal component. For example, if cobalt naphthenate is used as the sole additive, it has been found that an addition to rape oil in an amount between 0.1% and 5.0% by weight of cobalt napththenate, having a cobalt content of about 8% by weight, also raises the carbonization factor to the desired level. Another suitable additive is high vacuum bitumen which can, for example, be added to rape oil in an amount of 1.0% to 10.0% by Weight dissolved by an intermediate solvent such as dioctylphtalate.

An example of a lubricant formulation applied in accordance with the invention for the continuous casting of steel is as follows:

The casting apparatus was set up to continuously cast a bar of steel having a cross section of 115 x 115 mm. For this purpose steel having a carbon content of 0.2% was poured from a suitable vessel into a cooled oscillating open-ended mold and a casting containing a liquid steel core was continuously withdrawn from the mold at a rate of 2.4 meters per minute. The mold was lubricated by introducing a lubricant consisting of rape oil, to which was added 0.88% (by volume) lead naphthenate having a content of 30% by weight of lead. The quantity of the addition of the lead naphthenate could have been varied between 0.1% to 5.0% by weight depending upon the casting conditions. Whereas in the past casting produced under the same conditions and using 0.07 liter of rape oil per metric ton of steel without any such addition resulted in a noticeable amount of sticking of the steel in the corners and at the mold surfaces, no such undesirable sticking of the steel occurred when the rape oil was used with the aforesaid addition of lead naphthenate under otherwise the same conditions. When using a rape oil lead naphthenate combination in accordance with this invention the amount of lubrican required may be reduced to 0.04 liter of rape oil per metric ton of steel without causing flaws due to insufficient lubrication. By thus being able to provide good lubrication with about half the amount of lubricant previously required considerable economy is achieved. Moreover by thus being able to lubricate with less lubricant the surface of the casting is better and the formation of pores due to hydrogen absorption is less, and the lead naphthenate, which dissolves in the rape oil, does not form deposits in the oil pipes so that metering and distribution of the lubricant present no difiiculties. In addition, owing to the reduced rate of lubricant supply, visibility into the interior of the mold is improved since there is less smoky flaming.

What is claimed is:

1. A method of lubricating the casting mold during the continuous casting of metals, which comprises introducing into the casting mold a lubricant consisting of at least two components, one of which is a major component, and the other of which is an additive present in a minor amount, said additive being soluble in said major component and being effective to increase the proportion of carbon containing constituents in the residues formed in the mold by pyrolytic decomposition of the lubricant due to the heat of the metal being cast, said major component being a lubricating oil selected from the group consisting of vegetable oils, animal oils and mineral oils, and said additive being selected from the group consisting of lead napthenate, cobalt naphthenate, and manganese naphthemate.

2. The method of claim 1 in which said lubricating oil is rape oil.

3. The method of claim 1 in which said lubricating oil is rape oil and in which said additives is lead naphthenate from about 0.1% to about 5.0% by weight, said lead naphthenate having a lead content of about 30% by weight.

4. The method of claim 3 for lubricating a continuuous casting of steel having a carbon content of about 0.2% and being withdrawn from the mold at a rate of about 2.5 meters per minute, which includes introducing said rape oil and incorporated lead naphthenate into the mold at a rate of about 0.04 liters per metric ton of steel.

5. The method of claim 1 in which said lubricating oil is rape oil and in which said additive is cobalt naphthenate from about 0.1% to about 5.0% by weight having a cobalt content of about 8% by weight.

6. The method of claim 1 in which said lubricating oil is rape oil and in which said additive is high vacuum bitumen from about 1.0% to about 10.0% by weight, said high vacuum bitumen being dissolved in an equal amount of solvent prior to addition to the rape oil.

References Cited UNITED STATES PATENTS 1,231,259 6/1917 Johnson, Jr. -130 2,151,285 3/1939 Towssaint 252-37 2,258,930 10/1941 Haefner et a1. 252-59 2,456,824 12/1948 Fischer 252-37 2,837,791 6/1958 Tessmann 164-73 3,223,635 12/1965 Dwyer et a1 252-56 OTHER REFERENCES Grause et al.: Chemical Technology of Petroleum, 3rd ed. (1960), pp. 580 to 585.

DANIEL E. WYMAN, Primary Examiner W. H. CANNON, Assistant Examiner US. Cl. X.R. 

